In the prior art, a geared transmission capable of changing a gear stage thereof stepwise, and a continuously variable transmission capable of varying a speed change ratio steplessly are available as a transmission mechanism for transmitting power between rotary members. For example, a belt-type continuously variable transmission and a toroidal-type continuously variable transmission are known as the continuously variable transmission. Specifically, the belt-type continuously variable transmission is a transmission varying a speed change ratio continuously using a pair of drive pulleys and a pair of driven pulleys, and a driving belt applied to those pulleys. The known endless driving belt used in such belt-type continuously variable transmission is prepared by arranging a plurality of plate members called an “element” or a “block” in a circular manner while connecting the plate members with one another, and fastening the interlinked plate members by an annular belt called a “band” or a “carrier”.
When the driving belt of this kind applied to the drive and driven pulleys is driven by driving the drive pulley, a frictional force acts on a contact portion between the element and the drive pulley, and a compressive force is applied to the elements in the arranging direction thereof, i.e., in the thickness direction thereof according to a torque of the drive pulley. The compressive force applied to the element being contacted with the drive pulley is transmitted to the element being contacted with the driven pulley via the elements existing between the drive and driven pulleys. When the compressive force is transmitted to the element being contacted with the driven pulley, a frictional force is generated at the contact portion between the element and the driven pulley, and a torque to rotate the driven pulley is established according to the transmitted compressive force. The power is thus transmitted between the drive and driven pulley through the driving belt.
One example of above-explained driving belt is disclosed in Japanese Patent Laid-Open No. 2000-249195. The “High-Loaded Transmission Belt” taught by Japanese Patent Laid-Open No. 2000-249195 is composed of a center belt and blocks reinforced against lateral pressure, and it is applied to a main prime mover and an auxiliary prime mover of automobiles and agricultural machineries. Specifically, the “High-Loaded Transmission Belt” comprises a block (i.e., an element) which is so constituted that two belt sides having lock parts in its top end are connected to each other in their bottom ends by a connecting member, and two rows of endless carriers (i.e., rings) fixedly fitted into an engagement groove opening between the lock parts. The belt side portion of the element is provided individually with a convex portion and a concave portion on each face so that the elements can interlink with one another. Therefore, the interlinked elements can be aligned even when the belt is running.
In addition to above, Japanese Patent Laid-Open No. 2001-193796 discloses an invention relating to “Element for Metal Belt and Metal Belt” for continuously variable transmissions of vehicles. The metal belt taught by Japanese Patent Laid-Open No. 2001-193796 comprises: a metal endless band (i.e., a ring) applied to annular grooves of a drive and a driven pulleys; a plurality of metal element composed of a body portion to be contacted with the annular groove of the pulley, a pair of pillars erected on the body portion and faced with each other, an engagement protruded portion formed on a leading end of the pillar, and an opening for inserting the band (i.e., a recessed portion) formed between the engagement protruded portions; and an endless metal falling preventing body somewhat wider than the band. The falling preventing body can be bent to narrow its width when it is inserted in between the engagement protruded portions to prevent falling of the band.
According to the transmission belt taught by Japanese Patent Laid-Open No. 2000-249195, the lock parts are formed on both belt sides of the element erected beside the carriers to hold the carriers on the element, and the convex portion and the concave portion are formed individually on an upper corner of each face of the belt sides to interlink adjoining elements. That is, the convex portion and concave portion functioning as male and female connections are formed symmetrically on both upper corner of the element. The carriers are individually fitted into each engagement groove and held by the lock part so that two rows of the belts are held in the element.
According to the transmission belt of Japanese Patent Laid-Open No. 2000-249195 thus structured, the carriers arranged parallel to each other have to be overlapped partially when fitted onto the elements or dismounted from the elements. That is, a total width of the carriers arranged parallel to each other have to be reduced narrower than the opening width between the lock parts of the element when the carriers are fitted onto the elements or dismounted from the elements, by twisting the carriers to overlap partially.
In order to twist the carriers being arranged parallel to each other thereby overlapping those carriers partially, it is necessary to swing the interlinked elements, that is, to pivot the elements relatively with each other. However, according to the transmission belt taught by Japanese Patent Laid-Open No. 2000-249195, the convex portion and the concave portion for interlinking adjoining elements are formed on both upper corners of the element. Accordingly, lateral movement of the element has to be restricted. This makes difficult to overlap the carriers arranged parallel to each other when assembling the transmission belt.
In order to solve the above-mentioned problem, the applicant has filed an application relating to the driving belt, in which a male connection and a female connection for joining adjoining elements are individually formed on each face of the element being opposed to the adjoining element at a width center of the element. Therefore, each element can pivot relatively with the adjoining elements so that the two rows of rings aligned parallel to each other can be overlapped partially when fitted with the elements. However, the pivotal movement of the element is eventually restricted especially at a final phase of such fitting operation of the rings and the elements, for example, at a stage when fitting a last piece or last several pieces of the interlinked element with the rings. Thus, the last piece or last several pieces of the interlinked element is difficult to be fitted with the rings. That is, further modification of the element is still required to improve easiness in assembly of the driving belt.